I would also like to read some opinions or studies on this. Is 2-3 hours enough or does the minimum/near-minimum temp. have to be sustained for, say 8 hours or so? Currently, I am "chilling" my terrarium nightly with 4 freezer cold packs when the lights turn off. This drops the temps to 61-62 F, but I believe this drop only lasts ~ 3 hours or so. Anybody?
The time spent at max/min temps would be relative to whatever type of plants you have unless there are plants that have specific needs for max/min temps to be, say, 2 hours while catts/phals may need 8 hours.
in the greenhouse, soon as the sun hits it the temp zooms up to the maximum of 95 within an hour....and stays there to the nite cools it off....nite temps dip to 60 degrees and stay there for approx 8-9 hrs this time of year,....i grow a wide variety of orchids, placement in the greenhouse depending on microclimates....dens and cats and vandas taking the brunt of the heat and hot spots with paphs and phals in the cooler sections....and they all seem to thrive!